In recent years, a new regionalism in East Asia has been rapidly proceeding on the future development of an economic community in the region. Why have the East Asian nations taken a significant step toward pursuing the new regionalism? At the most basic levels, there are the three main factors relating to the world economy that are relevant to this issue. The first factor is increasing uncertainty about the future of a multilateral framework under the WTO. The Doha Development Agenda held in Doha, Qatar in November 2001, still fails to reach an agreement for concluding negotiations among the 151 members of WTO (as of January 2008). The second factor is the strengthening and expansion of EU in Europe, and the creation of NAFTA in North America and the enlargement of Pan-Americanism. The deepening and widening of trade blocs in Europe and North America caused the East Asia nations huge concern that their exports would face fierce competition due to the large markets of EU and NAFTA. The third factor, which is a catalyst in considering issues of the new regional integration in East Asia, is East Asian Financial Crisis of 1997-98. The financial crisis fostered a new belief that the East Asian nations need to band together so that the contagious spread of crises could be minimized by creating a regional financial framework. In order to make the development of their economic community more crucial and advanced, the East Asian nations are currently beginning to deepen economic and financial partnership with other nations in the region. However, there are so many obstacles to be overcome in the region before such a regional collaboration could become a reality. As East Asia is described as the “heterogeneity,” there are enormous diversities among the nations in terms of country size, ethnicity, religion, language, social and political structures, and the economic development in the region. Compared to Europe, for example, East Asia is characterized by greater diversity in term of size, the level of economic development, industrial structures, the depth of financial markets, and broad institutional frameworks. In addition, political rivalries, historical animosities, cultural differences and ideological confrontation still continue to provide the region with barriers to regional integration. Regardless of a wide range of diversities and difficulties emerged in the entire region, however, the East Asian nations are now undertaking its development of the future regional integration that would bring the huge prosperity to the region so that they could benefit from such a regional collaboration by creating a viable framework for closer cooperation and deeper integration. It was the eighth ASEAN+3 Summit in Vientiane, Laos on November 2004 that Leaders of ASEAN Member Countries, China, South Korea and Japan convened the first East Asian Summit (EAS) in Malaysia in 2005, and the EAS continues to contribute to creating a common understanding in East Asia by addressing the issues of regional integration from various angles. In addition, going beyond EAS, ASEAN sets up its blueprint for the ASEAN Economic Community (AEC) that transforms ASEAN into a single market and production base, highly competitive and fully integrated into the global community by 2015. This is the moment when the East Asian nations come together to participate in regional integration with a common conviction, and make valuable contributions on the regional development while tackling with so many challenges. It is because it would lay the foundation for the East Asian prosperity.